Polymeric foam is finding increasing application in the construction industry. However, under some conditions the foam may be subject to insect infestation, and particularly termite infestation. There is a need for methods of rendering polymeric foams resistant to insects.
U.S. Pat. No. 5,194,323 issued Mar. 16, 1993 and U.S. Pat. No. 5,270,108 issued Dec. 14, 1993, both assigned to AFM Corporation, disclose and claim polymeric foams suitable for construction purposes which have been treated with a borate compound to inhibit insect and, particularly, termite infestation. The patent does not teach or suggest that the insecticide could be added to the polymeric beads concurrently with the blowing agent.
U.S. Pat. No. 5,704,172 issued Jan. 6, 1998, assigned to The Dow Chemical Company teaches a rigid polymer foam having a plurality of grooves crossing in diagonal configuration which facilitates the application of insecticides to such rigid foam. The foam may be used for construction purposes. The patent teaches an external post fabrication application of insecticide and does not suggest that the insecticide may be incorporated into the polymer beads concurrently with the blowing agent.
Chemical Abstracts of Japanese Kokai 10036549 A2 published Feb. 10,1998, and Japanese Kokai 63254143 published Oct. 20, 1988 teach applying anti-termite agents to the exterior of foams. The abstracts do not teach or suggest incorporating the insecticides into the polymer beads concurrently with impregnation with the blowing agent.
The Chemical Abstract of French Patent 2698632 published Jun. 3, 1994, teaches the production of very light weight foams, preferably polyurethanes having a density from 5 to 20 g/l. While the patent teaches polyurethanes are preferred, it also teaches that the foam may comprise polystyrene, polyacrylates, and polycarbonates. The disclosure suggests the active substances are preferably introduced into the mixture before polymerization. However, examples 1 and 4 of the patent illustrate the invention using polystyrene foam. The active ingredient is not introduced into the monomer but rather is introduced into "a viscous but liquid styrene prepolymer which has been prepared by heating at 60.degree. C. for an unspecified period of time a mixture of 1000 g of styrene monomer, 1 g of benzoyl peroxide and 70 g of tributyl phosphate as a plastifier". MALATHION is added to the resulting prepolymer. The temperature is adjusted to 45.degree. C. and the mixture is stirred while nitrogen is bubbled through the mixture to obtain a foam having a specific weight of 12 g/l. The patent neither teaches nor suggests that the active ingredient could be incorporated into polymer beads concurrently with impregnation with a blowing agent.
Chemical Abstract of Japanese Kokai 63264670 A2 published Nov. 1, 1988 teaches impregnating polystyrene beads with boron compounds. The abstract of Japanese Kokai 63264670 A2 teaches that beads prepared by a bulk or emulsion polymerization are wetted with water and impregnated with boric acid. The abstract does not teach or suggest that the polymeric beads could be concurrently impregnated with blowing agent and insecticide.
Chemical Abstract of Japanese Kokai 63159451 A2 published Jul. 2, 1988 teaches impregnating polystyrene beads with compounds selected from the group consisting of Phoixom, Fenitrothion, Cyanophos, Acephate and Prothiophos, concurrently with impregnation with a blowing agent. However, the active ingredients do not appear to be soluble in the blowing agent as the impregnation takes place using a solvent or an auxiliary solvent for the active ingredient together with the blowing agent. The present invention has eliminated the solvent or auxiliary solvent which is necessary in accordance with the Japanese Kokai.
Chemical Abstract of Japanese Kokai 63152648 teaches impregnating an expandable polystyrene bead with 2 ppm of Chloropyrifos. This teaches away from the present invention as the bead is an expandable bead (i.e. already impregnated with blowing agent). Further the amount of insecticide is less than that of the present invention.
None of the above art discloses concurrently impregnating polymeric beads with blowing agent and an insecticide in the absence of a solvent.